pawsplay
Hero
D&D came by its wizards via Jack Vance. The same swords-and-sorcery literary tradition also gave us Howard and Moorcock's chaotic, reality-bending sorcerers. I think you can also thank Walt Disney for a good deal of what we consider a wizard. If you look at classic wizards, most of them would be not be wizards in D&D at all.
Merlin - Merlin is properly a druid or bard. In fact, if you read the older sources, he mostly prophesizes and changes his appearance, which would make him a very knowledge-focused member of the 3.5 Bard class. If you go by the Disney version, he looks more like a Sorcerer, spontaneous and insanely powerful, and taking full advantage of the Shapechange spell. Someone more knowledgeable will have to say what he would be in D&D 4e. I'm betting Wizard isn't it, though. Note also that in many versions, he is half demon but baptized, which would make him a half-fiend/cambion/something, technically.
Gandalf - Gandalf the Wizard. Of course, he's actually a powerful angel/deva who merely appears somewhat human. Assuming most of his amazing powers are actually class abilities and not angelic might, he looks most like a 3.5 Cleric or a 4e Invoker. Like many classic "wizards," he is handy with a sword.
Prospero - This magician from The Tempest uses a summoned spirit of the air to do his bidding and uses special robes and rituals to cast spells. No fireballs here. In 3.5, he might be a conjurer or a sorcerer, but in terms of his actual abilities, is probably a 3.5 cleric with the Summoning domain or a 4e Warlock/Invoker/something-not-a-wizard.
Merlin - Merlin is properly a druid or bard. In fact, if you read the older sources, he mostly prophesizes and changes his appearance, which would make him a very knowledge-focused member of the 3.5 Bard class. If you go by the Disney version, he looks more like a Sorcerer, spontaneous and insanely powerful, and taking full advantage of the Shapechange spell. Someone more knowledgeable will have to say what he would be in D&D 4e. I'm betting Wizard isn't it, though. Note also that in many versions, he is half demon but baptized, which would make him a half-fiend/cambion/something, technically.
Gandalf - Gandalf the Wizard. Of course, he's actually a powerful angel/deva who merely appears somewhat human. Assuming most of his amazing powers are actually class abilities and not angelic might, he looks most like a 3.5 Cleric or a 4e Invoker. Like many classic "wizards," he is handy with a sword.
Prospero - This magician from The Tempest uses a summoned spirit of the air to do his bidding and uses special robes and rituals to cast spells. No fireballs here. In 3.5, he might be a conjurer or a sorcerer, but in terms of his actual abilities, is probably a 3.5 cleric with the Summoning domain or a 4e Warlock/Invoker/something-not-a-wizard.